Statistics were published in 2019 Geotabwhich showed that the average decrease in the range of electric cars is 2.3% per year. This means that after about 10 years such a battery will reach 80% of its original range (it would be less than 9 years if we count on 2.3 percentage points). A new analysis has now been carried out which has shown that the decline in capacity has slowed slightly for cars and is now at 1.8% per year. It will thus fall to 80% after 12 years, to 70% even in 20 years, but this applies on the assumption that the drop will be the same every year. However, we know (and the study also points to this) that most lithium batteries show a faster decline at the beginning of operation, which then slows down significantly, with the capacity again starting to decline more rapidly towards the end of the battery’s life. That means a dead battery.
The graph shows that 5-year-old cars are on average at about 91% of their original capacity, while they usually range between 88 and 92%. Many factors affect the drop, age itself, temperature, working range (buffer size), charging speed, number of cycles, chemical mixture, cooling and the BMS itself. The study focused on some of these parameters.
When it comes to ambient temperatures, a mild climate is clearly better for batteries than too hot. There it was shown that after 4 years in a mild climate the capacity dropped to an average of about 96%, while in warmer areas it was 90%. Geotab also mentions the effect of cooling, where liquid is better than air, which was shown in the Tesla Model S and the 2015 Nissan Leaf, where the former’s battery dropped to 90% after 5 years, while the Leaf was at just over 80%. Here, however, I think that the study has big gaps and it cannot be attributed only to the cooling, as there are other factors. For example, the Tesla has a longer range (i.e. fewer cycles for the same distance) and also a different chemical mixture, which could also have contributed to the better result and could even have been the primary factor.
The interesting thing is that the high number of cycles (and high mileage) did not affect the degradation of the lithium cells much. Cars that drove less than 8,000 km per year were at around 92-93% after 4 years, while cars that drove over 20,000 km per year dropped to around 90% over the same period. However, fast charging showed a larger effect, while not being entirely small. If the car had never seen a fast charger in its life, after 4 years it had an average of 90%, if it was on it at most 3 times a month, it was already about 85%, and in the case of frequent fast charging (more than 3 times a month) it got to 81%. Again, however, it is necessary to take into account the fact that there are other influences. E.g. the cars that are on the fast charger more often are probably the ones that drive longer distances, so the effect of a higher number of cycles is added here.
Source: www.svethardware.cz
